Coated ammonium perchlorate and propellant compositions



United States Patent Ofiice 3,1937% Patented June 22, 1965 3,190,776COATED AMMONHUM PERtIl-ILORATE AND PROPELLANT COMPUSRTIDNS Hans H.Ender, Bufialo, N.Y., assignor to Union Carbide Corporation, acorporation of New York No Drawing. Filed Nov. 14, 1960, Ser. No. 68,614

41 Claims. (Cl. 1498) This invention relates to treated ammoniumperchlorate and, more particularly, to organosiloxane-coated ammoniumperchlorate.

Solid propellant composition containing ammonium perchlorate as anoxidizing agent and a solid organic polymer as a fuel have been employedheretofore to supply thrust for rocket engines. Such solid propellantcompositions have been produced by mixing ammonium perchlorate andliquid organic compounds that can be converted to solid organicpolymeric fuels and then converting the hardenable mixtures so formed insuitably-shaped molds to produce solid propellants of the desired shape.The solid propellants so produced contain ammonium perchlorate dispersedin a matrix of a solid organic polymer which thus functions as a binderfor the ammonium perchlorate as well as a fuel.

The above-described hardenable mixturesare often diflicult to prepare,since ammonium perchlorate is not readily wetted by various liquidorganic compounds that can be converted to solid organic polymericfuels. In addition, suchknown hardenablemixtures and the solidpropellants produced therefrom suffer from one or more seriousshortcomings. By way of illustration, the hardenable mixtures possesspoor rheological properties in that they can not be readily introducedinto molds (e.g., they do not pour readily). As a further illustration,the molded solid propellants produced from such hardenable mixturesoftentimes contain voids and are cracked, mechanically Weak anddisintegrate during storage owing to the depolymerization of the organicpolymeric fuels that form the matrices. As further illustration, theabovedescribed solid propellants have fixed Specific Impulse valueswhich limit the performance or" the engine in which they are used andthey have relatively high temperature sensitivities which necessitatetheir use in undesirably heavy engines.

It is an object of this invention to provide ammonium perchlorate whichhas been so treated that hardenable mixtures containing the treatedammonium perchlorate and liquid organic compounds that are convertibleto solid organic polymeric fuels canbe readily formed owing to thewetting of the treated ammonium perchlorate by the liquid organiccompound.

Other objects of this invention are to provide harden- Still anotherobject of this invention is to provide am monium perchlorate which hasbeen so treated that it imparts to solid propellants wherein it isincorporated increased Specific Impulse value and lower temperaturesensitivities.

This invention provides ammonium perchlorate coated with anorganosiloxane comprising groups represented by the formula:

RnSiO wherein R is a monovalent hydrocarbon group and n has a value from1 to 3 inclusive. This invention further provides hardenable mixturescontaining the coated ammonium perchlorate of thi invention and a liquidorganic compound that can be converted to solid organic polymeric fuel.This invention still further relates to solid propellant compositionsproduced from such hardenable mixtures and to processes for producingthe coated ammonium perchlorate, the hardenable mixtures and the solidpropellant compositions of this invention.

Illustrative of the monovalent hydrocarbon groups represented by R inFormula 1 are the linear alkyl groups (for example the methyl, ethyl,propyl, butyl, and amyl groups),.the cyclic alkyl groups (for examplethe cyclohexyl and cyclopentyl groups), the linear alkenyl groups (forexample the vinyl and the allyl groups), the cyclic alkenyl groups (forexample the cyclopentenyl and the cyclohexenyl groups), the aryl groups(for example the phenyl and naphthyl groups), the alkaryl groups (forexample the tolyl group), and the aralkyl groups (for example the benzyland beta-phenylethyl groups).

The organosiloxane that forms the coating on the coated ammoniumperchlorate of this invention can be linear, cyclic, or cross-linkedinstructure. The linear organosiloxa'nes include those containing onlygroups represented by Formula 1 wherein n is 2 (e.g., hydroxylendblocked dimethylpolysiloxanes, HO[(CH SiO] H) as well as thosecontaining only groups represented by Formula 1 wherein n is 3 (e.g.,hexamethyl disiloxane). The linear organisiloxanes also include thosecontaining both groups represented by Formula 1 wherein n is 2 andgroups represented by Formula 1 wherein n is 3 [c.g. trimethylsiloxyend-blocked dimethylpolysiloxanes, (CH SiO[CH SiO] Si(CI-I The cyclicorganosiloxanes contain only groups represented by Formula 1 wherein nis 2 (e.g., dimethylsiloxane cyclic trimer and tetramer). 'Thecross-linked organosiloxanes are those containing groups represented byFormula 1, at least some of which are those wherein n has a value of 1(e.g., methyl polysiloxane). In Formula 1 R can denote the same ordifferent groups on the same silicon atom or throughout a givenorganosiloxane molecule. Thus, suitable organosiloxan'es include thecompounds:

0 H 0 H V (CHs)aSiO S 10 S iO Si(CH )s and CH C 11 (01193810 S iO SiOSi(CH orr=o11 4 H 4 The coated ammonium perchlorate of this inventiioncan be produced by contacting ammonium perchlorate with anorganohalosilane having the formula:

RSiCl (3) wherein R' is a methyl, ethyl, vinyl, amyl, or phenyl group.More specifically, these preferred organotrichlorosilanes aremethyltrichlorosilane, 'ethyltrichlorosilane, vinyltrichlorosilane,amyltrichlorosilane, and phenyltrichlorosilane. The organosiloxancsproduced from 3 these preferred organotrihalosilanes comprise groupsrepresented by the formula:

wherein R has the above-defined meaning. More specifically, theseorganosiloxanes are the methylsiloxanes, ethylsiloxanes, vinylsiloxanes,amylsiloxanes, and phenylsiloxanes.

The organohalosilane represented by Formula 2 are uniquely suited foruse in the production of the coated ammonium perchlorate of thisinvention. That is, although other hydrolyzable silanes (e.g.,organoalkoxysilanes) can be converted to organosiloxanes comprisinggroups represented by Formula 1, the coated ammonium perchlorateproduced with such other hydrolyzable silanes i not satisfactory (e.g.,the coating does not adhere to the ammonium perchlorate). Withoutwishing to be bound by any particular theory, it appears that theorganosilanes represented by Formula 2 possess the ability to becomeproperly oriented on the surface of the ammonium perchlorate and so theorganosiloxanes produced from the organohalosiianes may be mechanicallylocked on the surface of the ammonium perchlorate owing to penetrationinto any irregularities on the surface and may be chemically linked tothe surface of the ammonium perchlorate (such as by hydrogen bonds). Onthe other hand, other hydrolyzable silanes (e.g., organoalkoxysilanes)apparently do not possess the ability to become properly oriented on thesurface of the ammonium perchlorate and so coatings formed therefrom arenot as securely bonded to the surface and readily separate therefrom.

The particular manner in which ammonium perchlorate is treated withorganohalosilanes in accordance with the process of this invention(i.e., treatment in the presence of water so that an organosiloxane isproduced on the surface of the ammonium perchlorate) is critical in providing coated ammonium perchlorate possessing the improved propertiesset forth herein. Other methods of treating ammonium perchlorate withorganohalosilanes (e.g., contacting ammonium perchlorate and anorganohalosilane under anhydrous conditions) fail to produce theimprovement in the properties of the ammonium perchlorate such as areattained by the process of the invention.

In producing the coated ammonium perchlorate of this invention, theammonium perchlorate can be brought into contact with theorganohalosilane in the presence of water by any convenient method. Byway of illustration, the organohalosilane can be vaporized and the vaporcan be passed through a bed of ammonium perchlorate. Preferably,however, the ammonium perchlorate is brought into contact with theorganohalosilane by forming a mixture of the ammonium perchlorate and asolution containing the organohalosilane dissolved in a suitablesolvent. The relative amount of ammonium perchlorate and solution is notnarrowly critical and so dispersions composed of relatively smallamounts of ammonium perchlorate dispersed in relatively large amounts ofthe solution can be employed. Preferably, however, the mixture is apaste composed of a relatively large amount of ammonium perchlorateblended with a relatively small amount of the solution (e.g., from to 90parts by weight of the solution per 100 parts by weight of the ammoniumperchlorate). Such organohalosilane solutions can contain from 0.1 partto parts, or preferably from 0.5 part to 5 parts by weight of theorganohalosilane per 100 parts by weight of a solvent. Suitable solventsare liquid organic compounds that dissolve the organohalosilanes andthat are non-reactive with the organohalosilanes and ammoniumperchlorate. Suitable solvents include the aliphatic hydrocarbons (e.g.,heptane and octane) and the aromatic hydrocarbons (e.g., benzene andtoluene).

In producing the coated ammonium perchlorate of this invention, it isessential that the organosiloxane comprising groups represented byFormula 1 is formed on the surface of the ammonium perchlorate. If theorganosiloxane is not formed on the surface of the ammonium perchlorate,the organosiloxane will not adhere to the ammonium perchlorate and aheterogeneous mixture of ammonium perchlorate and the organosiloxane,rather than ammonium perchlorate coated with the organosiloxane, isproduced. By way of illustration, if a solution containing a preformedorganosiloxane dissolved in one of the above-mentioned solvents is mixedwith ammonium perchlorate and the solvent is volatilized, there isproduced a heterogeneous mixture of ammonium perchlorate and theorganosiloxane.

One method of insuring that the organosiloxane comprising groupsrepresented by Formula 1 will be formed on the surface of the ammoniumperchlorate in producing the coated ammonium perchlorate of thisinvention is by forming a mixture of ammonium perchlorate and a solutioncontaining an organohalosilane dissolved in a solvent of theabove-described type and then bringing air that is laden with watervapor (e.g., air having a relative humidity of 40-90%) into contact withthe mixture. The air can be at an elevated temperature so as to serveboth as a means of bringing the water vapor into contact with themixture and as a means for volatilizing the solvent.

Another method of insuring that the organosiloxane consistingessentially of groups represented by Formula 1 will be formed on thesurface of the ammonium perchlorate in producing the coated ammoniumperchlorate of this invention is by absorbing a small amount of water onthe ammonium perchlorate and then mixing the ammonium perchlorate with asolution containing an organohalosilane dissolved in a solvent of theabovedescribed type.

Hydrolysis and condensation reactions occur during the formation of theorganosiloxane coating on the surface of the ammonium perchlorate by theabove-described methods. These reactions can be represented by theequations:

wherein X is a halogen atom. These reactions occur spontaneously, evenat temperatures below room temperature, but they are accelerated byelevated temperatures.

The temperature employed in either of the above-described methods ofinsuring that the organosiloxane comprising groups represented byFormula 1 will be formed on the surface of the ammonium perchlorate inproducing the coated ammonium perchlorate of this invention is notnarrowly critical. Thus, temperatures of from 0 C. to 150 C. are useful,but temperatures from 50 C. to C. are preferred. Other temperatures canbe used but no commensurate advantage is gained thereby.

After the ammonium perchlorate is coated with an organosiloxanecomprising groups represented by Formula 1 as described above, it can beseparated from any excess water, organohalosilane or froin the solventused in treating solution and from the hydrogen halide (HX) formed inthe hydrolysis reaction by any suitable means (e.g., by filtration or byreducing the pressure over the system to volatilize the water, hydrogenhalide, organotrichlorosilane, and/or solvent).

It is particularly desirable to remove the hydrogen halide from thecoated ammonium perchlorate since the hydrogen halide may have adeleterious effect on the solid propellant compositions produced fromthe coated ammonium perchlorate (e.g., the hydrogen halide may promotethe decomposition of the solid organic polymer that forms the matrix ofthe propellant composition). Gne method is allowing the coated ammoniumperchlorate 1 size.

convenient sequence. pounds that are solidified by curing, the mixing ofthe 5 to remain exposed to the atmosphere and to allow the hydrogenhalide to volatilize.

The amount of the organosiloxane in the coated ammonium perchlorate ofthis invention is critical in order to produce satisfactory solidpropellant compositions therefrom. The coated ammonium perchlorate mustcontain at least 0.01 part but no more than 5.0 parts by weight(preferably from 0.1 part to 3.0 parts by weight) of the organosiloxaneper 100 parts by weight of the ammonium perchlorate. Lesser amounts ofthe organesiloxane coating result in incomplete coating of the ammoniumperchlorate, which in turn seriously impairs the rheological and moldingproperties of hardenable mixtures containing the coated ammoniumperchlorate and a liquid organic compound that can be converted to asolid organic polymeric fuel; Greater amounts of the organosiloxanecoating seriously reduce the Specific Impulse values of solid propellantcompositions. Ammonium perchlorate having a particle size from 4 to 325mesh (Standard Screen Size) is particularly useful. Although ammoniumperchlorate having other particle sizes can be used in solidpropellantfuel compositions, no commensurate advantage is gainedthereby.

When the coating on the coated ammonium perchlorate of this invention isa methylsiloxane or a vinylsiloxane, it has been unexpectedly found thatthe bulk density of the coated ammonium perchlorate is greater than thebulk density of the uncoated ammonium perchlorate from which it wasproduced. This surprising property of arm monium perchlorate coated withmethylsiloxanes or vinylsiloxanes is a decided advantage since, byvirtue of this property, more of the ammonium perchlorate in the coatedform can be introduced into a storage chamber of a given In addition, byvirtue of this property, more of the ammonium perchlorate in the coatedform can be mixed with a liquid organic compound that can be convertedto a solid organic polymeric fuel before loss of the continuous phase ofthe liquid organic compound occurs. This increase in bulk density is notobserved in the case of ammonium perchlorate having, for example, anethylsiloxane, an amylsiloxane, or a phenylsiloxane coating. The lattercoated ammonium perchlorates have bulk densities that are about the sameas the bulk density of the uncoated ammonium perchlorate from which theyare produced.

The hardenable mixtures of the invention that are used to produce solidpropellant compositions of this invention contain the coated ammoniumperchlorate of this invention and a liquid organic compound that can beconverted to a solid organic polymeric fuel.

The hardenable mixtures of this invention can be produced by simplymixing the components together in any In the case of liquid organiccomcomponents of these hardenable mixtures is preferably conducted atroom temperature to minimize any premature curing of the liquid organiccompound. On the other hand, where the liquid organic compound is apolymer that is solidified by cooling (e.g., asphalt), the mixing isconducted at a temperature sufficiently elevated .to maintain thepolmyer in the liquid state. If desired, various plasticizers (e.g., atoluene sulfonamide-formaldehyde reaction product) can be added to themixtures to assist in obtaining thorough mixing of the components.

tures of this invention include thermoplastic polymers that have beenliquefied by heat as well as liquid monomer and liquid partial polymersthat can be cured to produce thermoplastic or thermoset solids (e.g.,resins or elastomers). Such fuels are materials that are readilyoxidized to liberate relatively large volumes of gas. Such liquidorganic compounds include phenol-formaldehyde polymers that are in the Astage, asphalt, liquid thioether polymers, liquid urethane etherpolymers, liquid partially cured alkyd resins, alkyl-substitutedphenol-formaldehyde polymers that are in the A stage, aryl-substitutedphenolformaldehyde polymers that are in the A stage, liquid plasticizedpolyvinyl acetal compositions containing a suflicient amount of aurea-formaldehyde or melamineformaldehyde condensation product to makethe composition thermosetting, liquid melamine-formaldehyde condensationproducts, liquid substituted melamine-formaldehyde reaction products,and liquid alkyd-vinyl heteropolymers. Preferably, such liquid organiccompounds have a viscosity from 50 to 10,000 centipoises at 25 C. tofacilitate the incorporation of the coated ammonium perchlorate therein.Specific liquid organic compounds include an air blown asphalt that hasa penetration with a gram weight for four seconds at 77 F. of 12-20 anda softening point of 230 F.240 F., tertiary-'butyl phenol-formaldehydepolymers that are in the A stage, tertiary-amyl phenylformaldehydepolymers that are in the A stage, alkydstyrene heteropolymers that arein the A stage, alkyd-styrene heteropolymers, and the product of thealkaline-catalyzed condensations of one mole of phenol and two moles offormaldehyde having a viscosity of 1000 centipoises at 25 C. By apolymer that is in the A stage as employed herein is meant that thepolymer is partially cured but is still liquid and capable of furthercuring.

The relative amount of the coated ammonium perchlorate and theabove-described liquid organic compound present in the hardenablemixtures of this invention can be varied widely, depending upon suchfactors as the particular liquid organic compound employed and thedesired burning characteristics of the solid propellant compositionproduced from the hardenable mixture. Generally, from 30 parts to partsby weight of the coated ammonium perchlorate per 100 parts by weight ofthe liquid organic compound are useful. Although other relative amountsof these liquid organic compounds can be employed, no commensurateadvantage is gained by employing such other amounts.

The hardenable mixtures of this invention can contain other ingredientsin addition to the coated ammonium perchlorate and the above-describedliquid organic compounds. Such other ingredients can be added, forexample, to accelerate the cure of those liquid organic compounds whichare curable, to provide additional fuel, to improve even further themoldability of the hardenable mixtures and/or to improve even furtherthe burning characteristics of the solid propellant composition producedfrom the hardenable mixtures. By way of illustration, compounds andmixtures of compounds such as chromium sesquioxide, ferrosoferric oxide,ZnO, Fe O TiO SnO A1 0 and CuO can be added to increase the burning rateof solid propellant composition produced from the hardenable mixtures.As a further illustration,

metals and compounds, such as aluminum, lithium aluminum hydrides, andammonium picrate can be added to the hardenable mixtures to provideadditional fuel.

The solid propellant compositions of this invention are produced'byhardening the above-described hardenable mixtures of this invention. Themethod used to harden any particular mixture is dependent upon the typeof liquid organic compound in the mixture. By way of illustration, whenthe liquid organic compound is a normally solid thermoplastic resin(e.g., asphalt) which is in the liquid state because it was maintainedat an elevated temperature above its melting point to allow for theincorporation of the coated ammonium perchlorate therein, hardening canbe accomplished simply by allowing the mixture to cool to roomtemperature. As a further illustration, when the liquid organic compoundis an uncured or partially cured heat-curable compound that can be curedto form a normally solid thermoplastic resinous fuel, the hardening canbe accomplished by curing the liquid organic compound at elevatedtemperatures to form a liquid polymer and allowing the mixture to coolto room temperature. As a further illustration, when the liquid organiccompound is an uncured or a partially cured compound that can be curedto form a solid thermoset resinous fuel, the hardening can beaccomplished by simply curing the liquid organic compound to produce theresinous fuel. The hardening of the hardenable mixtures of thisinvention converts the mixtures into solid propellant compositionscontaining the coated ammonium perchlorate of this invention dispersedin a matrix of a solid organic polymeric fuel.

The hardening of the hardenable mixtures of this invention is preferablyperformed after the hardenable mixture has been introduced into a moldthat is designed to mold the mixture into the shape required by theconfiguration of the particular combustion chamber in which the solidpropellant composition is to be employed. Owing to the usually excellentrheological properties of these hardenable mixtures, they can begenerally readily introduced into such molds by any suitable means(e.g., by simply pouring or by pressure injection). Such excellentrheological properties are possessed by all of those mixtures whereinthe coating on the ammonium perchlorate is an organosiloxane composed ofgroups represented by Formula 4.

Curing of those hardenable mixtures of this invention which containliquid organic compounds that are curable can be accomplished by anysuitable means, which means are governed by the particular curablecompound in the mixture. Some such curable mixtures can be cured simplyby allowing them to stand at room temperature. Generally, however, it isdesirable to accelerate the cure by heating the curable mixture. Theparticular temperature to which the curable mixture is heated to effectthe cure will, of course, be dependent on the particular curable liquidorganic compound in the mixture and on the presence or absence of acuring catalyst in the mixture. Cure temperatures from 60 C. to 150 C.are often suitable but other cure temperatures can be employed ifdesired.

The solid propellant compositions of this invention are generally freeof voids and cracks and in addition they are usually mechanically strongand do not deteriorate on standing owing to the depolymerization of thesolid organic polymer that serves as a fuel and a binder or owing to anyother cause. Such compositions often have increased Specific Impulsevalues and lower temperature sensitivities as compared to otherwiseidentical compositions wherein the ammonium perchlorate is uncoated.These advantageous properties are possessed by all of the solidpropellant compositions of this invention wherein the coating on theammonium perchlorate is an organosiloxane composed of groups representedby Formula 4.

The solid propellant compositions of this invention can be treated invarious conventional ways to improve their properties even further or toprovide special effects. By way of illustration, a restrictive liner canbe produced on the surface of the composition other than the surfacewhich it is desired to burn in the combustion chamber of rocket enginesin which it is to be employed. The restrictive liner insures that onlythe unlined surface burns.

The coated ammonium perchlorate of this invention has been describedabove in connection with its use in producing, ultimately, solidpropellant compositions. It should be noted, however, that theusefulness of the coated ammonium perchlorate is not limited to suchcompositions, but rather, the coated ammonium perchlorate can beemployed in other applications (e.g., in blasting compositions and thelike). In the latter applications,

the coated ammonium perchlorate need not be in particulate form, andother than the above-indicated amounts of the organosiloxane coating canbe present per parts of the ammonium perchlorate.

The following examples illustrate the present invention.

Example 1 Eight grams of finely divided ammonium perchlorate having aparticle size of 30 to 350 mesh were stirred with 3.2 grams of asolution containing 5 parts by weight of vinyltrichlorosilane dissolvedin 100 parts by weight of toluene to provide 2 parts by weight ofvinyltrichloro- 'silane per 100 parts by weight of the ammoniumperchlorate. The wet paste which was formed was well stirred andtransferred to an evaporating dish where it was allowed to stand exposedto air at 40-50% relative humidity for one hour. During this intervalthe toluene evaporated and the vinyltrichlorosilane became hydrolyzed todeposit a coating of vinylsiloxane (i.e., a silox-ane composed of CHCHSiO groups) on the ammonium perchlorate. After the one hour period,tests made with pH test paper showed no acidity (i.e., no HCl) waspresent. The last traces of toluene were removed by placing the materialin a vacuum desiccator and evacuating to 2 to -3 millimeters of mercurypressure for 30 minutes. Coated ammonium perchlorate so produced was afreeflowing powder as compared to the non-flowing original Nl-L ClO andit contained about 0.3 part by weight of the vinyls-iloxane per 100parts by weight of the ammonium perchlorate.

Example 2 This was a repetition of the above example except that 98grams of ammonium perchlorate were treated with a solution of 2 grams ofvinyltrichlorosilane in 38 grams of toluene. On this larger scale theprocedure was as before until it came to complete removal of the tolueneafter completion of the hydrolysis step. I'he material was heated for 30minutes at 100 C. before vacuum drying in order to finally remove thelast traces of the toluene. The treated material was then found to beidentical with that produced before.

Example 3 Nine hundred eighty grams of ammonium perchlorate having aparticle size of 30 to 350 mesh were treated with a solution of 20 gramsof vinyltrichlorosilane in 380 grams of toluene. The mixing was carriedout in a large evaporating dish, using a stirrer having a large Teflonblade. A slow stream of air at 40% relative humidity was passed over themixture while it was stirred to evaporate the toluene and hydrolyze thevinyltrichlorosilane. After it became reasonably dry, the material Wasallowed to stand in the dish without continuous stirring, but beingagitated occasionally with a spatula until all signs of acidity (i.e.,HCl) had disappeared, about 30 minutes. After this interval, thematerial was screened through a 3 0 mesh screen and heated for 30minutes at 100 C. in an air circulating oven, and then allowed to coolin a vacuum desiccator at 2 to 3 millimeters of mercury pressure. Thetreated material was a fine, very mobile powder which produced clouds ofdust when moved, and which splashed like water when shaken. The hull:density was measured and found to be 1.408 grams per cubic centimetercompared with 1.087 grams per cubic centimeter for untreated material,an increase of 37%. Analysis of the coated ammonium perchlorate showedthat it contained 0.18 part of the vinylsiloxane coating per 100 partsby weight of the ammonium perchlorate.

Example 4 This example is identical with Example 3 except that 20 gramsof methyltrichlorosilane were used in place of 20 grams ofvinyltric'hlorosilane, and the amount of toluene reduced to 300 grams toreduce the evaporation time. The final material was again a very mobilepowder with a bulk density of 1.389 grams per cubic centimeter. Analysisshowed that a coating of 0.34 part of the methylsiloxane (i.e., asiloxane composed of CH SiO groups) per 100 parts by weight of theammonium perchlorate had been produced on the ammonium perchlorate.

Example 5 When ammonium perchlorate was coated with an ethylsiloxane(i.e., a siloxane composed of C H SiO groups), the coated ammoniumperchlorate was .found to have a bulk density of 1.360 grams per cubiccentimeter.

Example 6 This example is identical with Example 4 with the exceptionthat 20 grams of phenyltrichlorosilane were used in place of themethyltrich'lorosilane. The final material was less free-flowing andcontained many lumps which were'then crushed in a mortar. The bulkdensity was very close to that of untreated ammonium perchlorate, namely1.0755 grams per cubic centimeter. Analysis showed 1.0 part ofphenylsiloxane (i.e., a siloxane composed of C H Si groups) coating per100 parts by weight of the ammonium perchlorate.

Example 7 When 100 parts by weight of asphalt are melted, 50 parts byweight of ammonium perchlorate coated with 0.5 part of a vinylsiloxaneare mixed with the melted asphalt to produce a hardenable mixture andthe mixture so formed is placed in a suitably shaped mold and is allowedto solidify by cooling, there is produced a solid propellant compositionof this invention.

Example 8 This example is also identical with Example 4 except that 20grams of amyltrichlorosilane were used in place of 20 grams ofmethyltrichlorosilane. This material showed less tendency to compactthan the material described in Example 5 but had a lower bulk density,1.064 grams per cubic centimeter. Analysis showed 0.7 part of a coatingof amylsiloxane (i.e., a siloxane composed of groups) per 100 parts byweight of the ammonium peraddition, such mixtures, when cured to a solidstate, will be characterized by stability during storage and by improvedphysical properties. On the other hand, untreated ammonium perchlorate,when added to a liquid partial polymer which when cured serves as a fueland binder for solid propellants produces a mixture that possesses poorrheological and molding properties. That is to say, thorough admixturesof the uncoated ammonium perchlorate and partial polymers are difiicultto obtain and, moreover, that the mixtures are of high viscosity and arediflicult to mold or shape. The physical properties of solid propellantsprepared from untreated ammonium perchlorate are characterized byinstability during storage and by poor physical properties.

When ammonium perchlorate is treated with organoalkoxysilanes (as forexample vinyltriethoxysilane) and I preformed organosiloxanes (as forexample a dimethylsiloxane oil) in the manner described above andsubsequently mixed with partial polymer fuels, the resulting admixtureis also characterized by poor rheological properties. In addition,little or no improvement is obtained in the stability and physicalproperties of solid propellants prepared from ammonium perchlorate socoated.

10 Example 9 Ten grams of powdered ammonium perchlorate and a solutioncontaining 0.2 gram of phenyltrichlorosilane and 0.2 gram ofethyltrichlorosilane that are dissolved in 5 grams of benzene can beblended to form a paste. The paste so formed can be placed in an opendish and air that has been heated to 50 C. and that has a relativehumidity of 50% can be brought into contact with the paste (e.g., it canbe passed over the dish) to hydrolyze the silanes and to volatilize thebenzene. There is so produced ammonium perchlorate that is coated withfrom 0.1 to 3.0 parts by weight per parts by weight of the ammoniumperchlorate of a copolymeric organosiloxane composed of phenylsiloxygroups (i.e., C H SiO groups) and ethylsiloxy groups (i.e., C H SiOgroups). The coated ammonium perchlorate so produced is separated fromany remaining benzene and the hydrogen chloride formed in the hydrolysisof the silanes by heating at 100 C.

The latter example illustrates the production of ammonium perchloratecoated with organosiloxanes composed of difierent types of siloxanegroups represented by Formula 1. The production of ammonium perchloratehaving such coatings is accomplished by employing a mixture of suitableorganohalosilanes represented by Formula 2 in the coating processgenerally described above. The mesh and the Standard Screen Sizereferred to herein have reference to particle sizes determined inaccordance with the National Bureau of Standards Sieve Numbers.

Each monovalent hydrocarbon group represented by R in Formula 1desirably contains from 1 to 10 carbon atoms.

What is claimed is:

1. Coated ammonium perchlorate wherein the coating is an organosiloxanecomprising groups represented by the formula:

wherein R is a monovalent hydrocarbon has a value of l.

2; Coated particulate ammonium perchlorate .wherein the coating is anorganosiloxane consisting essentially of groups represented by theformula:

wherein R is a member selected from the group consisting'of methyl,ethyl, vinyl, amyl, and phenyl groups and wherein the coating is presentin amount of from 0.1 part to 3.0 parts by weight per 100 parts byweight of the ammonium perchlorate.

3. The coated ammonium perchlorate of claim 2 wherein R is a methylgroup.

4. The coated ammonium perchlorate of claim 2 wherein R is an ethylgroup.

5. The coated ammonium perchlorate of claim 2 wherein R is a vinylgroup.

6. The coated ammonium perchlorate of claim 2 wherein R is an amylgroup.

7. The coated ammonium perchlorate of claim 2 wherein R is a phenylgroup.

8. The coated ammonium perchlorate of claim 2 wherein the ammoniumperchlorate has a particle size from 40 to 350 mesh.

9. A hardenable mixture comprising particulate ammonium perchlorate thatis coated with an organosiloxane comprising groups having the formula:

group and n wherein R is a monovalent hydrocarbon group and n has avalue of 1, said coating being present in an amount from 0.1 to 3.0parts by Weight per 100 parts by weight of ammonium perchlorate and aliquid organic compound that can be cured to form a solid organicpolymeric fuel.

10. The hardenable mixture of claim 9 wherein the thermosetting liquidorganic compound is asphalt.

11. The hardenable mixture of claim 9 wherein the liquid organiccompound is a phenol-aldehyde polymer that is in the A stage.

12. The hardenable mixture of claim 9 wherein the liquid organiccompound is liquid partially cured alkyd resin.

13. The hardenable mixture of claim 9 wherein the liquid organiccompound has a viscosity from about 500 to about 10,000 centipoises at25 C.

14. A hardenable mixture comprising particulate am- 1 monium perchloratethat is coated with an :organosiloxane comprising groups having theformula:

wherein R is a member selected from the group consisting of the methyl,ethyl, vinyl, amyl, and phenyl groups, said coating being present in anamount from 0.1 to 3.0 parts by weight per 100 parts by weight ofammonium perchlorate; and a thermosetting liquid organic compound thatcan be cured to form a solid thermoset resinous fuel.

15. The hardenable mixture of claim 14 wherein R is a methyl group.

16. The hardenable mixture of claim 14 wherein R is an ethyl group.

17. The hardenable mixture of claim 14 wherein R is a vinyl group.

18. The hardenable mixture of claim 14 wherein R is an amyl group.

19. The hardenable mixture of claim 14 wherein R is a phenyl group.

20. A solid propellant composition comprising coated particulateammonium perchlorate that is coated with an organosiloxane comprisinggroups represented by the formula:

wherein R is a monovalent hydrocarbon group and n has a value of 1, saidcoating being present in an amount of from 051 to 3.0 parts of weightper 100 par-ts by weight of ammonium perchlorate and a solid organicpolymeric fuel which serves as a matrix for the coated particulateammonium perchlorate.

21. The solid propellant composition of claim wherein the ammoniumperchlorate has a particle size of from 40 to 350 mesh.

22. The solid propellant composition of claim 20* wherein the solidorganic polymeric fuel is asphalt.

23. The solid propellant composition of claim 20 wherein the solidorganic polymeric fuel is a cured phenolaldehyde polymer.

24. The solid propellant composition of claim 20 wherein the solidorganic polymeric fuel is a cured alkyd resin.

25. A solid propellant composition comprising coated particulateammonium perchlorate that is coated with an organosiloxane comprisinggroups represented by the formula:

RSiO

wherein R is a member selected from the group consisting of methyl,ethyl, vinyl, amyl, and phenyl groups, said coating being present in anamount of from 0.1 to 3.0 parts by weight per 100 parts by weight ofammonium perchlorate; and a solid organic polymeric fuel which serves asa matrix for the coated particulate ammonium perchlorate.

26. The solid propellant composition of claim wherein R is a methylgroup.

27. The solid propellant composition of claim 25 wherein R is an ethylgroup.

wherein R is a monovalent hydrocarbon group and n has a value of 1,which comprises contacting ammonium perchlorate with an organohalosilanehaving the formula:

wherein R and n have the above-defined meanings and X is a halogen atom,in the presence of water to produce said organosiloxane on the surfaceof the ammonium perchlorate.

32. A process for producing coated ammonium perchlorate wherein thecoating is an organosiloxane comprising groups represented by theformula:

wherein R is a member selected from the group consisting of methyl,ethyl, vinyl, amyl, and phenyl groups, which comprises contactingammonium perchlorate with an organohalosilane having the formula:

RSiCl wherein R has the above-defined meaning, in the presence of waterto produce said organosiloxane on the surface of the ammoniumperchlorate.

33. A process for producing coated ammonium perchlorate wherein thecoating is an organosiloxane comprising groups represented by theformula:

wherein R is a monovalent hydrocarbon group and n has a value of 1, saidprocess comprising forming a mixture of ammonium perchlorate and asolution containing an organohalosilane that is represented by theformula:

wherein R and n have the above-defined meanings and X is a halogen atomthat is dissolved in a liquid organic compound that is a solvent for theorganohalosilane and that is nonreactive with the organohalosilane andammonium perchlorate; and bringing air that contains water vapor intocontact with said mixture to produce the coated ammonium perchlorate.

34. A process for producing coated ammonium perchlorate wherein thecoating is an organosiloxane com prising groups represented by theformula:

wherein R is a member selected from the group consisting of methyl,ethyl, vinyl, amyl, and phenyl groups, said process comprising forming amixture of ammonium perchlorate and a solution containing anorganohalosilane that is represented by the formula:

R'sic1 wherein R has the above-defined meaning which is dissolved in aliquid organic compound that is a solvent for the organohalosilane andthat is non-reactive with the organohalosilane and ammonium perchlorate;and bringing air that contains Water vapor into contact with saidmixture to produce the coated ammonium perchlorate.

13 35. A process for producing coated ammonium perchlorate wherein thecoating is an organosiloxane comprising groups represented by theformula:

RnSiO wherein R is a monovalent hydrocarbon group and n has a value of1, said process comprising absorbing water on ammonium perchlorate andforming a mixture containing the ammonium perchlorate which has waterabsorbed thereon and a solution containing an organohalosilanerepresented by the formula:

R SiX wherein R and n have the above-defined meanings and X is is ahalogen atom that is dissolved in a liquid organic compound that isnon-reactive with the organohalosilane and ammonium perchlorate; andbringing air that contains water vapor into contact with said mixture toproduce the coated ammonium perchlorate.

36. A process for producing coated ammonium perchlorate wherein thecoating is an organosiloxane comprising groups represented by theformula:

RSiO

wherein R is a member selected from the group consisting of methyl,ethyl, vinyl, amyl, and phenyl groups, said process comprising absorbingwater on ammonium perchlorate and forming a mixture containing theammonium perchlorate which has water absorbed thereon and a solutioncontaining an organohalosilane represented by the formula:

RSiCl wherein R has the above-defined meaning that is dissolved in aliquid organic compound that is a solvent for the organohalosilane andthat is non-reactive with the organohalosilane and ammonium perchlorate;and bringing air that contains water vapor into contact with saidmixture to produce the coated ammonium perchlorate.

37. A process for producing a hardenable mixture that can be convertedto a solid propellant composition, said process comprising forming amixture containing coated particulate ammonium perchlorate wherein thecoating is an organosiloxane comprising groups represented by theformula:

wherein R is a monovalent hydrocarbon group and n has a value of 1, saidorganosiloxane being present in an amount of from 0.1 to 3.0 parts byweight per 100 parts by Weight of ammonium perchlorate; and a liquidorganic compound that can be cured to form a solid organic polymericfuel.

38. A process for producing a hardenable mixture that can be convertedto a solid propellant composition, said process comprising forming amixture containing coated particulate ammonium perchlorate wherein thecoating is an organosiloxane comprising groups represented by theformula:

RSiO

wherein R is a member selected from the group consisting of methyl,ethyl, vinyl, amyl, and phenyl groups, said organosiloxane being presentin an amount of from 0.1 to 3.0 parts by weight per 100 parts by weightof ammonium perchlorate, and a liquid organic compound that can be curedto form a solid organic polymeric fuel.

39. A process for producing solid propellant compositions, said processcomprising hardening a mixture containing coated particulate ammoniumperchlorate wherein the coating is of an organosiloxane comprisinggroups represented by the formula:

RnSiO T wherein R is a monovalent hydrocarbon group and n has a value of1, said organosiloxane being present in an amount of from 0.1 to 3.0parts by weight per 100 parts by Weight of ammonium perchlorate, and aliquid organic compound that can be cured to form a solid organicpolymeric fuel.

40. A process for producing solid propellant compositions, said proces-scomprising hardening a mixture containing coated particulate ammoniumperchlorate wherein the coating i-s of an organosiloxane comprisinggroups represented by the formula:

RSiO wherein R is a member selected from the group consisting of methyl,ethyl, vinyl, amyl, and phenyl groups, said organosiloxane being presentin an amount of from 0.1 to 3.0 parts by weight per 100 parts by weightof ammonium perchlorate, and a liquid organic compound that can be curedto form a solid organic polymeric fuel.

41. The process of claim 32 wherein the silane that is brought incontact with the ammonium perchlorate is in the vapor phase.

References Cited by the Examiner UNITED STATES PATENTS 2,532,201 11/50Sprague 117-100 2,595,465 5/52 Keene et al.

2,605,194 7/52 Smith.

2,857,258 10/58 Thomas 149-19 2,929,697 3/ Perry et al. 149-19 2,967,7891/61 Hoyt 117-100 2,999,744 9/61 Eckels 149-19 3,022,149 2/62 Cramer149-19 3,058,858 10/62 Batchelder 149-19 3,086,895 4/63 Schaefier et al.149-19 CARL D. QUARFORTH, Primary Examiner.

LEON D. ROSDOL, ROGER L. CAMPBELL,

Examiners.

40. A PROCESS FOR PRODUCING SOLID PROPELLANT COMPOSITIONS, SAID PROCESSCOMPRISING HARDENING A MIXTURE CONTAINING COATED PARTICULATE AMMONIUMPERCHLORATE WHEREIN THE COATING IS OF AN ORGANOSILOXANE COMPRISINGGROUPS REPRESENTED BY THE FORMULA: